To analyze the mechanisms of cell response against the mechanical stress, we examined the changes of cell growth, proliferation-related gene expressions and localization of cell adhesion molecules when the mouse osteoblast derived cells were cultured under different mechanical stress conditions. It had revealed that the progression of S phase in cell cycle showed a little delay when they were cultured under gravity vector-averaged clinorotation and, in contrast, it was hastened when the cells were cultured under centrifugation force. It is widely accepted that cell adhesion and/or cytoskeletons are closely related to the cell proliferation. Although we examined the gene expression of cell adhesion molecules, integrins, of the cells cultured under mechanical stress (60 G of centrifugation force) by RT-PCR, the gene expressions of integrin α1, α2, α5 and β1 did not changed. To examine whether the cell growth was also elevated when they were cultured under static pressure, instead of the centrifugation force, the cells seeded on a cover slip were inflicted the pressure (ca. 100 kPa) in a syringe for 24 hr. As the result, the growth rate of osteoblast-derived MC3T3-E1 cells was slightly elevated but it was not significant difference between the experimental group and the control group. Therefore, we analyzed the changes of localization and formation of one of the cell adhesion molecules, integrin β1, and cytoskeletons, such as microtubules and microfilaments using a confocal microscope. But no significant difference was observed among the cells cultured under the static pressure, centrifuged culture and the stationaly control. On the other hand, the cells cultured under clinorotaion seemed to slightly decrease the formation of microfilament.